On Tue, Dec 07, 2010 at 11:07:05AM +0100, Jean Delvare wrote: > The I2C specification explicitly describes both SDA and SCL as > bidirectional lines. An I2C master with a read-only SCL is thus not > compliant. If a slow slave stretches the clock, errors will happen, > so the bus can't be considered as reliable. > > Signed-off-by: Jean Delvare <[email protected]> > --- > drivers/i2c/algos/i2c-algo-bit.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > --- linux-2.6.37-rc5.orig/drivers/i2c/algos/i2c-algo-bit.c 2010-12-07 > 11:02:38.000000000 +0100 > +++ linux-2.6.37-rc5/drivers/i2c/algos/i2c-algo-bit.c 2010-12-07 > 11:03:23.000000000 +0100 > @@ -604,9 +604,10 @@ static int __i2c_bit_add_bus(struct i2c_ > int (*add_adapter)(struct i2c_adapter *)) > { > struct i2c_algo_bit_data *bit_adap = adap->algo_data; > + int ret; > > if (bit_test) { > - int ret = test_bus(bit_adap, adap->name); > + ret = test_bus(bit_adap, adap->name); > if (ret < 0) > return -ENODEV; > } > @@ -615,7 +616,16 @@ static int __i2c_bit_add_bus(struct i2c_ > adap->algo = &i2c_bit_algo; > adap->retries = 3; > > - return add_adapter(adap); > + ret = add_adapter(adap); > + if (ret < 0) > + return ret; > + > + /* Complain if SCL can't be read */ > + if (bit_adap->getscl == NULL) { > + dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
I'll have a think about wording. I might be able to improve it. As a note, I always prefer cannot to can't. > + dev_warn(&adap->dev, "Bus may be unreliable\n"); if there are any other warnings, should we print just one unreliable warning at the end of the scan? -- Ben Q: What's a light-year? A: One-third less calories than a regular year. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
